The present invention relates to an improved structure of an air compressor waste drain valve having an automatic drain hole and a dust collector provided respectively at the center and circumference of the inside base of the drain valve so that the moisture produced by the air compressor can be stored in the dust collecting tank of a dust collector by means of a hollow filter and the dust produced by the air compressor can be overflown through the overflow port of the hollow cover plate, after the moisture has been accumulated to the sufficient level to ascend the float ball to drive the connecting rod gear, the water will be escaped automatically through the drain hole and the dust will be accumulated to a certain quantity and then can be drained for collection by means of opening the valve, so as to achieve the respective drainage effort for water and dust, thus on the one hand it can avoid the dust blockage in the automatic drain hole, on the other hand it can meet the environmental requirements against water pollution; furthermore, on the top of the overflow port an air pressure hose is provided and fixed on the opening of a vertical hole having a check valve inside and is connected with an air inlet, so that when the dust is adhered on the filter located in the overflow port, it needs not to be removed for cleaning, just simply fill the air from the air inlet to open the check valve and apply strong air pressure through the nozzle of an air pressure hose to the filter to remove the dust and let the dust be exhausted from the valve to achieve the convenient cleaning effect.
Referring to FIGS. 1 and 2, the air compressor of a conventional drain valve has to be arranged on the top position and installed on the bottom of an air storage tank, so that the air can continuously enter into the cup body D through the air inlet A1 of the cover A by means of the micro exhaust of the micro adjustment exhaust valve, the airflow will then be blocked by the distribution disk, on the one hand the dust will be blocked on the distribution disk B, on the other hand the water will flow to the bottom of the cup body, however, the dust will be also taken along by the water and flown to the bottom of the base D, since the semi-spherical piston head F1 of the piston rod F is still plugged on the cushion G1 of the drain hole G, the water is going on accumulation until the float ball E is slowly ascending and finally drives the connecting rod H to move the actuating rod H1 and to activate the air inlet pipe connector to move downwards to release the air outlet C1 from the blockage of diaphragm B2, at this moment the airflow will enter the diaphragm chamber C2 through the air outlet pipe connector to make the diaphragm B2 be compressed upwards to ascend the piston rod F as well as to compress the compression spring B1, the said semi-spherical piston head F1 will then leave the drain hole G to drain the water from the drain hole G automatically, at the same time the piston rod F will be returned rapidly by means of the compression spring B1 to make the said semi-spherical piston head F1 return to the cushion G1 position and block the drain hole, at this moment the said float ball E will be descended and activate the connecting rod H, thus the return spring H2 by means of its return elasticity after stretching will drive the actuating rod H1 to actuate the air outlet pipe connector C to ascend to make the air outlet C1 return and be blocked by the diaphragm B2 to achieve the automatic drainage. However, because of the frequency of the vertical displacements of the said piston rod F as well as the fluctuation of the airflow and the water, the piston rod F will be easily deflected while reversing, thus the center of the semi-spherical piston head F1 will be impossible to return exactly on the cushion G1 and produces a clearance, as a result a big quantity of airflow will be escaped from this clearance, therefore, not only the moisture and dust of the air produced by the air compressor can not be filtered but also the air pressure output will be also considerably reduced; furthermore, much quantity of dust (e.g. rusty chips from the air storage tank of the air compressor, sands etc.) will be contained in the produced air pressure and will be easily to be blocked on the distribution disk B and drain hole G, as a result insufficient air pressure will b entered into the cup body D and will be impossible to thrust the diaphragm B2 to drive the piston rod F moving upwards to drain the water, even the semi-spherical piston head F1 will produce leakage due to the blockage of dust. In addition to the above mentioned drawbacks, such design can only be installed in suspension or horizontal position and is impossible to be installed vertically.